Generally, a transit system is a large-scale public transportation system serving a given area, typically comprising buses, subways, and elevated trains. A transit system usually has numerous transit lines which represent pathways through the given area from a starting point to an ending point through various intermediate stopping points. One or more transit vehicles can service a particular transit line, generally several times a day.
Express transit lines, for example the transit lines serviced by express transit vehicles like express buses, sometimes consist of relatively few stops connected by route segments of significant length. Heavy traffic, lane blockages due to accidents, weather, and other factors can all affect the punctuality and reliability of these express transit vehicles. Despite the availability of current traffic information, generally express transit vehicles follow a fixed path irrespective of traffic conditions, and so riders of express transit vehicles must deal with low reliability/punctuality, and even cancelled trips, in response to conditions that cause longer delays.